Variable stroke mechanism for printing platen



Jan. 30, 1968 J. A. CRAFT ETAL 3,366,213

VARIABLE STROKE MECHANISM FOR PRINTING PLATEN Filed April 17, 1967 INVENTORS.

JAMES A. CRAFT JOHN 0. SCHAEFER ATTORNEY.

United States Patent Ofitice 3,366,213 VARIABLE STROKE MECHANISM FOR PRINTING PLATEN James A. Craft and John 0. Schaefer, Lexington, Ky., as-

signors to International Business Machines Corporation,

Armonk, N.Y., a corporation of New York Filed Apr. 17, 1967, Ser. No. 631,404 11 Claims. (Cl. 197-45) ABSTRACT OF THE DISCLGSURE A reciprocating character-by-character printing platen is driven through a variable length print stroke that is roughly proportional to the size of the image being printed to avoid possible smudging caused by platen overshoot. Also, selectable long and short print cycles are provided by alternate drive cams to increase the speed of printing smaller characters.

Cross reference to copending application Reference is made to U.S. patent application Ser. No. 631,308 entitled Printer Having Force Compensating Platen, filed simultaneously herewith by John O. Schaefer, which pertains to certain subject matter disclosed herein.

Disclosure of the invention Our concept of a variable stroke and variable cycle length drive for a reciprocating printing platen permits the construction of a reasonably sized, direct impression composing machine that can efficiently print characters within a wide size range.

Copending application Ser. No. 631,308 discloses an improved platen for printing, by direct impression, high quality characters within a large range of different sizes and shapes, as required for example to compose headlines for various purposes. We have found that if a platen is driven through a relatively long stroke, as required to print a large character, it can cause smudging during its overshoot when printing a small character. This problem is most acute where the character image masters are all mounted on a common base such as a disk and are positioned in close adjacency to make eificient use of available space. The stroke that is suitable for a single large character may cover the positions of several small character image masters on a disk.

Accordingly, this invention provides a drive member that is moved through a relatively constant predetermined motion increment during each printing cycle. The drive member is releasably coupled to the platen such that only a portion of its total motion increment is etfective to drive the platen. Information as to the character size, preferably carried by the character disk itself, controls the releasable coupling to provide an eifective platen stroke that is roughly proportional to the size of the character being printed. Character size information also can serve a further function of controlling the paper feed for proportional letter feeding, or the feed of an ink ribbon to maximize ribbon usage efficiency.

We have also found that the majority of printed material falls in the size range of 36 point or less which is considerably smaller than the occasionally required 72 point characters. Considerable time would be wasted if the machine had to cycle through all of the motion required to print the largest characters, when printing the smaller characters. Accordingly, this invention provides for the selection of either a long or a short printing cycle whereby the predetermined motion increment of the drive member can be substantially reduced for printing the smaller characters.

3,366,213 Patented Jan. 30, 1968 These and other objects, features, and advantages of our invention will be apparent to those skilled in the art upon reading the following description of a specific preferred embodiment of our invention, wherein reference is made to the accompanying drawings of which:

FIGURE 1 is a perspective over-all view of a headline printer of the type required to print characters within a wide range of sizes;

FIGURE 2 is an exploded perspective view of the principle operative elements of a headline printer embodying variable stroke and cycle mechanisms constructed in accordance with this invention; and

FIGURE 3 shows several actual samples of characters that have been printed by a machine like that of FIG- URE 1, illustrating the typical variation in size of characters to be printed.

Referring now more specifically to FIGURE 1 there is shown a pressure transfer headline printer 10 having a unitary character matrix, disk or plate D that is rotatably mounted by a hub 11 to permit the operator to seiectively position individual downwardly facing relieved or raised characters or symbol image masters D on its undersurface at a printing position 12. Also formed on or otherwise integrally interconnected with the undersurface of the disk D is a code disk D that provides a physical representation of the size of corresponding character image masters D Imaging media including a paper strip, web, or other record 13 is fed from an internal roll (not shown) past the printing position 12. The imaging media also preferably includes a pressure transfer ink ribbon 14 fed from an internal supply (not shown) between the disk D and the paper 13 to an internal ribbon takeup. In the preferred embodiment shown, the ribbon 14 is fed at right angles to the paper 13.

A printing operation is initiated by depression of print key 15 and is preferably accompanied by automatic paper and ribbon feeding in proportion to the size of the character printed. In addition, several ancillary controls are provided including a paper feed expand-contract control lever 20, an impression control level 16, and a print cycle control lever which forms part of this invention.

As more particularly disclosed in aforesaid application Ser. No. 631,308, and with reference to FIGURE 2, a print roll assembly or platen forms images on the paper 13 by pressing it against the ribbon 14 and a selected image master D Platen 40 travels a rectilinear path 41 defined by a pair of rails 42. From the size of the sample character images shown in FIGURE 3, it will be recognized that path 41 must be relatively long to accommodate large characters such as the 60 point characters C and C and must bequite short to avoid smudging of paper adjacent small characters such as 14 point character C It will also be recognized that considerable wasted motion would exist if path 41 were the same length for the large characters C and C as for the small charactfil' C3.

Stroke control Returning to FIGURE 2 it will be seen that motion of the platen 40 is transmitted thereto by a pivoting, reciprocatable drive bracket 43 having connecting slots 44 therein. The bracket 43 is powered by a pivotally movable drive member that is driven through a relatively constant predetermined motion increment 51 by a power cam 52 acting through follower 53 and linkage 54. Motion of the drive member 50 to the right stores energy in return spring 55 connected thereto by a link 56. Spring 55 drives the drive member 50 to the left in the latter part of a print cycle as permitted by a falling portion of the cam 52.

Drive bracket 43 is connected to the drive member 50 through a releasable latch or coupling that is normally retained against a latching surface 57 on the power member 50 by a light spring 61, and operates to transfer rightward motion of the drive member 50 to the drive bracket 43 thus carrying the platen 40 to the right during a printing stroke. As the latch 60 moves to the right with bracket 43 about shaft 45, its leftward end 62 moves upwardly and through a link 63 causes a control bracket 64 to rotate clockwise on shaft 45. Control bracket 64 has a holding surface 65 that engages a variably positionable stop hook 66 at a point in its travel representative of the size of the character being printed. Upon encountering stop hook 66, control bracket 64 will be held stationary against further rotation. Continued rightward motion of the latch 60 will cause a downward force to be induced at its leftward end 62 causing the latch 60 to pivot out of engagement with surface 57 and sever the connection between drive member 50 and the drive bracket 43. The drive member 50 continues its rightward motion to the extent of predetermined increment 51 while the drive bracket 43 and the platen 40 remain stationary, having completed the necessary motion for printing the selected character.

As the drive member 50 is returned leftwardly by spring 55 under the control of cam 52, it engages a restore tab 46 on the drive bracket 43 and moves platen 40 leftwardly to its home position. Latch 60 is also restored by spring 61 into cooperative engagement with latching surface 57 and the mechanism is prepared for a new operation.

As mentioned above, the stationary position of stop hook 66 is representative of the size of the character being printed. Obviously, a manual control could position the stop hook 66 to select any desired printing stroke. We prefer however to automatically select the printing stroke from the code disk portion D of the character matrix D, which also serves to control proportional letter feeding of the paper 13 as later disclosed. Code portion D is positioned in the path of a probe or finger 70 that is carried by an oscillating arm 71 and is pivoted counterclockwise into engagement with the underside of the matrix D by a light spring 72. Arm 71 pivots clockwise with shaft 73 as permitted by a pin 74 that permissively follows the motion of the link 56 by riding in a slot 56a therein. Pin 74 is connected to shaft 73 through a link 75 and a space control bracket 21 and is urged to follow link 56 by a spring 76. Space control bracket 21 also carries with it the stop hook 66 through a connection 77. As the drive member 50 and link 56 move to the right, pin 74 moves to the right and pivots bracket 21 and link 71 clockwise to move the probe 70 and stop book 66 to the right. At some point in its travel, probe 70 will encounter a ledge D of the code portion D that is dimensioned to be representative of the character image master D located at the print position 12. The ledge D prevents further movement of the probe 70 and thereby makes stop hook 66 stationary to cause release of latch 60 as described above.

Proportional letter feeding is accomplished through the use of much of the mechanism already described. The paper 13 is fed to the left after completion of a print stroke by counterclockwise rotation of feed roll or displacing means 80. During the print stroke, feed roll 80 is released from feed shaft 81 by disengagement of an infinite resolution cone clutch 82 by a control link 83. Control link 83 is operated from a clamp control cam 47 through motion of paper clamping means 48. Control link 83 separates a drive arbor 84 of the cone clutch 82 from feed roll 80 by pushing against the forward end of shaft 81 and against a spring 85. The shaft 82 and the drive arbor 84 mounted thereon are resiliently urged clockwise by a spring 86. The shaft 82 is gear connected to a frame supported pivotal sector 87 that transfers the motion of the pin 74 to the arbor 84 during the rightward motion of drive member 50 and link 56. In operation, sector 87 and drive arbor 84 are rotated counterclockwise during the print stroke until motion of the probe 70 is arrested by engagement with the code portion ledge D It will be understood that code ledge D permits drive arbor 84 to move an amount roughly equivalent to the character size. Upon completion of the print stroke, cam 47 releases the paper clamping means 48 and retracts control link 83 connected thereto to permit the arbor 84 of cone clutch 82 to drivingly engage feed roll 80. As the drive member 50 and link 56 move leftwardly, pin 74 is encountered, and through sector 87, drive arbor 84 is rotated counterclockwise through the same increment of motion that it rotated clockwise during the printing stroke to feed the desired amount of paper. It will be recognized that substantially identical mechanism can be provided to feed the ink ribbon 14 in increments generally proportional to the size of characters being printed. In fact, we prefer to provide such a control, however, the mechanism is not shown herein due to the identity of concept and structure involved. It also should be recognized that the stroke control via stop hook 66, control bracket 64 and latch can be combined with a proportional ribbon feed control instead of the proportional letter feed control if desired, and in such event, the printing stroke should be in the same direction as the ribbon feed.

The paper feed just described can be controlled to provide greater or lesser spacing between characters via manual control lever 20. Control lever 20 is connected by a pulley and cable transmission 22 to a miniature screw jack 23 acting against an anti-backlash spring 24 to vary the angular distance between separate halves 25 and 26 of the bracket 21. Separation of the bracket halves 25 and 26 moves probe to the left, thereby increasing its potential travel prior to encountering a code ledge D Conversely, bringing bracket halves 25 and 26 together moves the probe 70 to the right and reduces the potential motion thereof prior to encounter with the code ledge D Cycle length control As previously described, cam 52 causes power member 50 to move through a relatively long predetermined motion increment such as increment 51. For small characters, a shorter predetermined motion increment such as increment 58 is desirable and accordingly, a second power cam 59 is provided for driving follower 53 when printing small characters. Selection between cams 52 and 59 is accomplished by the cycle length control lever 30 which shifts a cam shaft 31 to either of two positions determined by a spring detent 32. Since less time is required for the drive member 50 to traverse the shorter motion increment 58, the cam 59 is made of two lobes whereby shaft 31 will produce a complete operat ing cycle in a half revolution. A two lobe cam 49 is also provided to operate the clamping means 48 through its entire motion in a half revolution of the shaft 31.

Power for rotating shaft 31 is derived from a motor or rotational energy source M that continuously drives shaft M and is interconnected with shaft 31 by print cycle control means 90 which includes a conventional spring clutch 91. A worm sleeve or pinion gear 92 connected to the output of spring clutch 91, drives a helical gear 33 that is slidably mounted on the shaft 31 by a key 34. Clutch 91 moves to a shaft interconnecting condition upon release by a latch 93 following depression of selectively operable print key 15 which rotates latch control link 94 clockwise to a release position and permits spring 95 to pull latch 93 to the right.

Control over rotation of shaft 31 to determine whether a full or half revolution cycle is performed is accomplished by a cycle control cam 96, which is shiftable with the shaft 31 to position either a full revolution or single lobe control surface 97 or a two lobe, half revolution Control surface 98 in operative relationship with a clutch restore bracket 99. As clutch 91 rotates the worm 92 to drive shaft 31, cycle control cam 96 rotates and at a proper time, drives restore bracket 99 counterclockwise to pivot the latch 93 back into arresting engagement with the clutch 91. For example, in a long cycle, worm 92 might make forty revolutions before latch 93 is driven to terminate the cycle. Shifting of cycle control cam 96 rightwardly to the short cycle position where control portion 98 is in operative engagement with bracket 99, causes the cycle to be cut in half and clutch latch 93 is restored after twenty revolutions of the worm 92 to disconnect the clutch 91.

Operation The mechanism described may be summarized with a review of a typical operation of the device. A character matrix D having the desired siZe and style of characters is selected and mounted onto the printer 10. The character size is noted and a slow or fast print cycle is selected by control lever 30 according to whether the character size is large or small respectively. The expandcontract control lever 20 is adjusted to select a desired relative letter spacing. A character is selected for printing by manually rotating the matrix D to position the desired raised image master D at the printing position 12. Suitable detent means (not shown) accurately positions and retains the matrix D in the selected position. By selecting the character for printing, the operator has automatically selected an appropriate ledge D of the code portion D to control the print stroke and paper feed. Similar selection of ribbon feed can be provided by similar means if desired.

The print key 15 is .now depressed to pivot control link 94 clockwise and release the clutch latch 93 to commence rotation of the cam shaft 31. Cam 47 is first to be effective and operates paper clamping mechanism 48 and paper feed release control link 83 to prepare for a print stroke. Cam 52 next becomes effective and pulls drive member 50 to the right carrying with it the platen 40 which traverses path 41 in pressure transfer cooperation with the selected raised image matter D Probe 70 driven by springs 76 and 86 follows the motion of drive member 50 until encountering the selected ledge D at which time latch 60 is operated by control bracket 65 to sever the connection between drive bracket 43 and drive member 50 and terminate the printing stroke. Encounter of the probe 70 with ledge D also terminates clockwise rotation of the paper feed clutch drive arbor 84 and thereby measures the desired paper feed. Drive member 50 continues to the full extent of its motion increment 51, as driven by cam 52. Cam 47 again becomes effective to release the clamping means 48 and to permit engagement of the paper feed clutch 82. Next cam 52 becomes effective and permits spring 55 to pull drive member 50 and link 56 to the left. The drive bracket 43 will be restored to the left as the drive member 50 engages tab 46 thereon. Also, paper will be fed by counterclockwise rotation of feed roll 80 as link 56 encounters pin 74 to return the motion of drive arbor 84 measured during the printing stroke.

Those skilled in the art will appreciate that we have provided an improved printer having a unique ability to accommodate a wide range of character sizes. While particular structure of a preferred embodiment has been disclosed to illustrate the concepts of our invention, it will be recognized that various modifications, additions, deletions and substitutions can be made in the specific structure shown without departing from the spirit and scope of our invention as defined by the appended claims.

What is claimed is:

1. A printer for printing variable sized images and including a platen supported adjacent a printing position for traversing a path in pressure transfer cooperation with a raised image master, wherein the improvement comprises:

a drive member,

means for moving said drive member through a relatively constant predetermined motion increment,

reciprocatable means drivingly connected with said platen,

releasable latch means normally providing an effective motion transfer connection between said drive member and said reciprocatable means, and operable upon release of said latch means to sever said motion transfer connection,

means for providing a representation of the size of the raised image master, and

means responsive to said size representation for operating said latch means after the platen has traversed the raised image master.

2. The printer defined in claim 1 wherein the further improvement comprises the drive member moving means having:

means for varying said predetermined motion increment.

3. The printer defined in claim 1 further including, displacing means for moving imaging media relative to said printing position to space adjacent print operation along said media, wherein the improvement further comprises:

means responsive to said size representation for controlling the amount of relative movement by said displacing means.

4. The printer defined in claim 1 wherein the image master is one of a plurality of masters mounted on a common matrix that is movable to position individual ones of said masters at said printing position, and said representation providing means includes a code portion forming part of said matrix and representative of the size of each individual image master, wherein the improvement further comprises:

a probe for sensing said code portion,

means operating said probe during movement of said platen, and

means responsive to said probe sensing said code portion of said matrix for operating said latch means.

5. The printing device defined in claim 1 wherein said representation providing means includes a code portion that is substantially integrally interconnected with said raised image master and is representative of its size, wherein the improvement further comprises:

a probe for sensing said code portion,

means operating said probe during movement of said platen, and

means responsive to said probe sensing said code portion for operating said latch means.

6. The printer defined in claim 5 further including displacing means ror moving imaging media relative to said printing position to space adjacent print operations along said media, wherein the improvement further comprises:

means responsive to said size representation for controlling the amount of relative motion by said displacing means.

7. The printer defined in claim 2 wherein further improvement comprises the drive member moving means having:

a continuously available source of rotational energy,

a rotatable shaft,

means for selectively interconnecting said source with said shaft,

a pair of power cams for translating rotation of said shaft into different increments of reciprocal motion, and

means for selectively, individually interconnecting said cams to said drive member.

8. The printer defined in claim 7 wherein said means for selectively interconnecting said source with said shaft includes a clutch, and control means retaining said clutch in a condition of disconnecting said source from said shaft and selectively operable to place said clutch in a condition of interconnecting said source with said shaft, said control means further including means responsive to a predetermined rotation of said shaft for returning said clutch to said disconnecting condition, and wherein the improvement further comprises:

means for varying the predetermined rotation to which said returni -g means responds.

9. A printer for printing variable sized images and including a platen supported adjacent a printing position for traversing a path in pressure transfer cooperation with a raised image master and including a rotatable shaft drivingly connected with said platen for moving it along the path, a continuously available source of rotational energy, a clutch for selectively interconnecting said source with said shaft, and control means normally retaining said clutch in a condition of disconnecting said source from said shaft and selectively operable to place said clutch in a condition of interconnecting said source with said shaft, said control means further including means responsive to a predetermined rotation of said shaft for returning said clutch to said disconnecting condition, wherein the improvement comprises:

means for varying the predetermined rotation to which said returning means responds.

10. The printer defined in claim 9 further including a reciprocatable drive member for transmitting motion from said shaft to said platen, wherein the improvement comprises:

a pair of power cams for translating rotation of said shaft into different increments of reciprocal motion, and

means for selectively, individually, interconnecting said cams to said reciprocatable drive member.

11. The printer defined in claim 10 wherein said returning means responds to either a relatively short predetermined rotation of said shaft or a relatively long predetermined rotation of said shaft, and said cams translate said shaft rotation into either a relatively short increment of reciprocal motion or a relatively long increment of reciprocal motion, and wherein the improvement further comprises:

control means interconnecting said predetermined rotation varying means and said selective cam interconnecting means whereby said relatively short shaft rotation is selected simultaneously with said relatively short reciprocal motion and said relatively long rotation is selected simultaneously with said relatively long reciprocal motion.

References Cited UNITED STATES PATENTS 1,357,090 10/1920 Hasbrouck 197---6.4 2,804,968 9/1957 Elliott et a1. 101-376 X 2,888,873 6/1959 Uhl et al 101-274 X 2,942,544 6/1960 Williams 101--269 3,277,991 10/1966 Weber et al. l976.4

ROBERT E. PULFREY, Primary Examiner.

WILLIAM B. PENN, Examiner.

E. S. BURR, Assistant Examiner. 

